This invention relates generally to adjusters for seats, and more particularly it relates to a vertical position adjuster for a motor vehicle seat of the type having a seat frame provided with swing supports hinged to a base frame and vertically adjustable relative to the latter by means of an adjusting device which includes adjusting gears arranged for engaging gear segments formed on the swing supports and being adapted for locking the same in the desired vertical position.
In a known vertical adjusting device of the aforedescribed type the input member of the gear unit consists of two gears arranged on a common shaft and engaging two gear segments formed on two swing supports in the front range of the seat; the gear segments are linked to the seat frame and connected via a coupling rod to swing supports arranged in the back range of the seat. The seat frame is thus connected to the base frame by the swing supports in each corner area of the seat. Upon actuation of the shaft which supports for joint rotation the gears acting as input members of the gear unit, all swing supports are simultaneously raised or lowered in accordance with the direction of rotation of the shaft. An adjusting lever is provided for the actuation of the adjusting shaft and is connected to the latter via a braking spring coupling by means of which the swing supports are positively held in their adjusted position when the adjusting lever is released. In such known vertical position adjusting devices all swing supports, according to the direction of rotation of the adjusting shaft, are either raised or lowered simultaneously, thus uniformly raising or lowering the seat frame. The disadvantage of such known adjusting devices, however, resides in the fact that it is impossible to adjust a different vertical position of the front part of the seat relative to its backrest part. In addition, the power drive for such conventional vertical position adjusters cannot be made without the employment of additional structural components such as braking spring coupling, for example.